Commercial raising of cattle for dairy production requires proper management. In addition to the various husbandry concerns such as herd health and nutrition, a critical management area for economic survival of any cattle operation, is the breeding management of the cows.
Dairy cows are managed intensely and there are costs associated with breeding the cow, how long it takes each cow to become pregnant, as well as associated labor costs. Economics of a dairy make it important to both minimize the amount of time a dairy cow is not pregnant and yet still have a high probability of the cow becoming pregnant.
It is estimated that for every day past a set goal date that a cow remains non-pregnant or open, there is an economic loss of between $1.00-$3.00 per day. An average sized dairy herd is between 200 to 1,000 cows. If the 24 hours during which the cow should be bred is missed for each cow, this represents an economic loss of $4,200.00 to $21,000.00 annually. Often cows are not successfully bred for as many as 3 estrous cycles, due to infertility, infections and semen-related problems. If one half of the cows in a herd of 200 to 1,000 is not impregnated for 3 cycles, the estimated economic loss increases to $6,300.00 to $31,500.00 annually. These projections of economic loss to the producer demonstrate the critical importance of the cow spending the majority of each year producing milk.
Annually 1 million dairy cows are culled for reproductive failure, for reasons such as infertility, and infections.
To improve the management of dairy cows and decrease the economic losses associated with the non-pregnant interval it is desirable to have additional options and management tools other than culling the animals.
There are several variables that can impact the whether or not the cow is successfully bred and becomes pregnant during any particular estrous cycle. The number of times that a cow must be bred before becoming pregnant is traditionally measured as the “service to conception rate.” The variables that affect the service to conception rate include semen quality (processing and handling), sperm quantity/quality, breeding technique, and egg quality; all of these variables play major roles.
Still, the most important variable remains in the timing of the insemination. If inseminated too early the sperm may not survive until the optimal 12 hour fertilization window. If inseminated too late the sperm will not reach their destination during the optimal window of time. Finally, if the animal was somehow identified for breeding but is not in estrus, then she will not become pregnant after insemination.
Some dairy producers try to improve this service to conception rate by being extremely conservative (relying on multiple signs of heat) before breeding an animal. While the rate can improve, this means of identification will allow for Type II errors (many cows that are actually in heat will not be bred and thus will miss one more cycle to become pregnant). If a producer decides to liberally breed animals (not on multiple signs) the tendency will be to use lower price semen and thus possibly reduce conception rates and/or decrease the rate of genetic improvement in the herd, group or dairy. Knowing exactly if a cow is in estrus and the best time to breed such animal is very important information to a dairy producer.
There are several easily observable, as well as biological signs that have been identified as indicators of estrus in cattle. Outward signs would include, in order of importance, observed mounting activity, evidence of mounting activity (roughened hair coat increased activity), abnormal social behavior with other animals and the change of appearance of the vulvar region. Biological changes that have been observed could include changes in the following; basal body temperature, mucus conductivity and reproductive hormone levels in blood, tissue and/or milk. The hormones that have the most effect and are most indicative of stage of the estrous cycle are luteinizing hormone, follicle-stimulating hormone, progesterone, estrogen and inhibin.
Currently, the best way to identify animals that should be scheduled for insemination is by identifying the animal in standing heat. This visual method generally requires a half hour observation session twice daily. Even with this concentrated effort, many cows will go unobserved.
Several devices and methods have been used by dairy farmers to aid in this visual observation effort. These methods basically try to mark an animal that has been mounted by another animal. Chin ball markers, dye-release mount detectors, and tail chalking are methods that still require the herd manager to observe the mark on the animal. Recently, there have been some electronic instruments developed to measure mounting activity. There are systems that include a glued-on transmitter that sends identification of mounting activity to a receiver. There are systems that include a glue-on electronic device which counts mounting activity and displays it cow-side. These electronic devices only monitor mounting successes, which by itself still provides for significant type I and type II errors (silent heat—loss of device—accuracy). Of even lesser value are pedometers which simply measure elevated cow activity. These are even less accurate than the mounting sensors.
There is still a need for more accurate and successful estrus detection, particularly in cows.